DECEMBER 2013 30-DAY OUTLOOK
555 PM EST Fri. Nov. 29, 2013
Atmospheric patterns, 700 MB and 500 MB height anomalies, statistical data, and various models such as the ECMWF monthly, NMME, IMME and the CFSv2, along with observed cases from past such months, data from 1895-2000 were used in this forecast.
Oceanic and atmospheric indices across the equatorial central Pacific continue to indicate neutral ENSO conditions. Sea surface temperature anomalies were near zero across much of the equatorial Pacific, with slightly above normal temperatures just west of the Date Line and slightly below normal temperatures near the South America coast. The low-level and upper-level winds are near normal across most of the equatorial Pacific. Convection over parts of Indonesia and the far western Pacific continue to be enhanced, while convection over the central Pacific remains suppressed. These atmospheric and oceanic conditions are consistent with neutral conditions. Statistical and dynamical models indicate that sea surface temperatures in the east-central Pacific are expected to be near normal for the next few months.
The MJO continued to become less active during the past week. The amplitude decreased as observed by the CPC velocity potential index, and there was no amplitude or eastward propagation depicted on the RMM index. Other tropical indices remain to be less active are dominating the anomalous convection and circulation patterns. Equatorial Rossby Wave activity is suggested with westward propagating areas of enhanced convection over the Maritime Continent and suppressed convection just west of the Date Line. An enhanced convective signal with fast eastward propagation over the Indian Ocean is currently interacting with the Rossby Wave over the Maritime Continent.
During Week-2, a majority of dynamical models indicate the possibility of an re-energized MJO over the Maritime Continent, although there is considerable uncertainty in the development of this pattern. Enhanced precipitation is anticipated to continue over the Maritime Continent, possibly spreading eastward along the equator. Suppressed convection is forecast to continue over the equatorial Indian Ocean.
The NAO is currently positive and is forecast to trend negative by day 7 and remain negative through day 14. The AO index is positive and is forecast to be generally positive to neutral through day 14. The PNA index is near neutral and is forecast to trend negative by day 7 and remains negative through day 4.
Most of the mean spatial anomalies forecast near to above normal temperatures for the nation. Half of the CFS ensembles members depict a ridge along or off the West Coast and a trough over the East. The others forecast a zonal flow across the nation. They also forecast below normal temperatures for most of the nation except for the southern U.S. and the Southeast. A trough is forecast over the West and a ridge is forecast near the Southeast coast.

Below normal temperatures are forecast for the Rockies. The probability of below normal temperatures for the region is 55 percent. Above normal temperatures are forecast for the lower Mississippi Valley, the Southeast and the lower Mid-Atlantic. The probability of above normal temperatures for this region is 55 percent. The remainder of the nation is not expected to exceed climatological values.

Above normal precipitation is forecast for the Northwest, the northern Rockies the southern Plains into the Mississippi Valley. The probability of above normal precipitation for the Northwest is 55% and 52% southern Plains into the Mississippi Valley. Below normal precipitation is forecast for the Southeast. The probability of below normal precipitation for this region is 55 percent. The remainder of the nation is not expected to exceed climatological values.

Jim Munley Jr.
http://www.jimmunleywx.com